TextBox inside checkbutton not wrapping

I have a listBox with a checkbox with inside a textblock:

<ListBox x:Name="lbxtgbTab3"  FontSize="{StaticResource BUTTON_FONTSIZE}"  HorizontalContentAlignment="Stretch"  Background="{x:Null}" BorderBrush="{x:Null}" FontWeight="Bold">
  <ToggleButton  Name="tgb4Tab3" Background="{x:Null}" Height="{StaticResource BUTTON_HEIGHT}" Click="ToggleButton_Click" Padding="0" FontWeight="Bold">
            <TextBlock Name="otb4Tab3" Text="4 - GESTIONE P.P." Margin="0" Background="Red" TextAlignment="Center" TextWrapping="Wrap"/>
  </ToggleButton>

now the problem is that it doesn't wrap as you can see in the picture